Gas masks have been used by the military since the beginning of World War I. Whereas they perform the basic function of protecting the wearer from gas and liquid agents, they have the following deficiencies.
Protection System: The present masks cover the face with butyl coated nylon which offers only six hours of liquid agent protection.
Decontamination: After a given exposure to contaminating gas, the entire mask has to be cleaned and there are limited provisions for hasty cleaning.
Recognition: Because the only transparent portion is in a small area about each eye, it is difficult to recognize the wearer by sight.
Field of View: The field of view is limited because the wearer's lenses contained in the mask are too far from the eyes, and it is extremely difficult for the wearer to look down.
Use With Weapon: The design of the optics of present weapons requires that the distance between the pupil of the operator's eye and the eyepiece of the weapon, which is termed eye relief, be 25 mm or less, but the eye relief for present masks is greater than this. Furthermore, the gas filter cannister and the hoses between it and the mask drastically interfere with the use of many weapons.
Optical Correction: In present masks, separate lenses ground to the wearer's prescription are mounted within the mask at a distance that is too far from the eye for best vision, and the lenses are too small.
Laser Protection: Protection against laser beams is provided by a specially coated outsert that is mounted in front of the correction lenses so as to further increase the eye relief.
Communication: The intelligibility of spoken words is far below that required for adequate communications.
Breathing Resistance: The resistance to inhaling is larger than desired primarily because of the construction of the filter cannister, but the necessary one way flapper exhalation valve also provides too much resistance.
Comfort: The buckles for retaining the mask on the head of the wearer become uncomfortable after a few hours so that the wearer often removes the mask before it is safe to do so.
Heat Burden: The face piece of the mask is comprised of impermeable materials and is not ventilated so that intolerable heat stress situations build up quickly in warm ambient temperatures.
Physical protection: Although limited protection is provided against the elements and branches, there is little or no protection against flying fragments.
Thus the state of the art gas masks are unsatisfactory in nearly every required function. They provide protection for too short a time, are difficult to decontaminate and are optically incompatible with weapons. In addition, it is difficult for one wearer to recognize or talk clearly to another. Furthermore, because of breathing resistance and heat buildup, the masks may be discarded before it is safe to do so.